Editor’s Note (1/7/21): We are republishing this story following the attack on the U.S. Capitol yesterday by right-wing extremists enabled by President Donald Trump. Some lawmakers are now calling on Vice President Mike Pence and the president’s Cabinet to invoke the 25th Amendment against Trump to remove him from office, citing the frightening prospects of his access to the nation’s nuclear codes. Scientific American argues that, no matter who is president, leaving the decision to launch nuclear weapons to one person is dangerous and should require a second opinion.

In just five minutes an American president could put all of humanity in jeopardy. Most nuclear security experts believe that's how long it would take for as many as 400 land-based nuclear weapons in the U.S. arsenal to be loosed on enemy targets after an initial “go” order. Ten minutes later a battalion of underwater nukes could join them.

That unbridled power is a frightening prospect no matter who is president. Donald Trump, the current occupant of the Oval Office, highlights this point. He said he aspires to be “unpredictable” in how he might use nuclear weapons. There is no way to recall these missiles when they have launched, and there is no self-destruct switch. The act would likely set off a lethal cascade of retaliatory attacks, which is why strategists call this scenario mutually assured destruction.

With the exception of the president, every link in the U.S. nuclear decision chain has protections against poor judgments, deliberate misuse or accidental deployment. The “two-person rule,” in place since World War II, requires that the actual order to launch be sent to two separate people. Each one has to decode and authenticate the message before taking action. In addition, anyone with nuclear weapons duties, in any branch of service, must routinely pass a Pentagon-mandated evaluation called the Personnel Reliability Program—a battery of tests that assess several areas, including mental fitness, financial history, and physical and emotional well-being.

There is no comparable restraint on the president. He or she can decide to trigger a thermonuclear Armageddon without consulting anyone at all and never has to demonstrate mental fitness. This must change. We need to ensure at least some deliberation before the chief executive can act. And there are ways to do this without weakening our military responses or national security.

This is not just a reaction to current politics. Calls for a bulwark against unilateral action go back more than 30 years. During the Reagan administration, the late Jeremy Stone, then president of the Federation of American Scientists, proposed that the president should not be able to order a first nuclear strike without consulting with high-ranking members of Congress. Such a buffer would ensure that actions that could escalate into world-destroying counterattacks would not be taken lightly. Democratic legislators recently introduced a law that would require not just consultation but congressional support for a preemptive nuclear attack. Whether or not that seems like the best check on presidential nuclear power is a matter for Congress.

We already know that second-check plans would not compromise American safety. Security experts used to worry that a hair-trigger launch was needed to deter a first strike by an enemy: our instant reactions would ensure that our opponent would feel catastrophic consequences of aggression. In the modern world, that is no longer the case. The U.S. has enough nukes in enough locations—including, crucially, our roving, nuclear-armed submarines—that nuclear strategists now agree it would not be possible to take out all of the nation's weapons with a first strike. The Pentagon, in a 2012 security assessment, said the same thing. It noted that even in the unlikely event that Russia launched a preemptive attack on the U.S.—and had more nuclear capability than current international agreements allow for—it “would have little to no effect on the U.S. assured second-strike capabilities.” That conclusion suggests that we will have ample firepower even if two or more people discuss how to use it.

We have come close to nuclear war in the past because of misidentified threats, including an incident in 1979 in which computers at a military command center in Colorado Springs wrongly reported the start of a major Soviet nuclear offensive. Ballistic and nuclear bomber crews immediately sprang into action. Crisis was averted only after satellite data could not corroborate the warning, and American forces finally stood down. In our March issue, Scientific American called for taking the U.S. nuclear arsenal off high alert because of this and other such near misses.

Taking the arsenal off high alert is an important step. But putting another check into the system—removing one person's unfettered ability to destroy the world—will create another essential, lasting safeguard for the U.S. and the planet.